Kunihito Tanaka*, Emi Yoshida, Tadaaki Inomata and Masuhiro Kogoma

Department of Chemistry, Faculty of Science and Technology, Sophia University
7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, JAPAN
t-kunihi@hoffman.cc.sophia.ac.jp

Titanium nitride (TiN) has good chemical and physical characteristics. In the case of using TiN as the protective layer of titanium metal, TiN is usually prepared by heat treatment, PVD and CVD. However, those methods have some problems. Therefore there are few practical examples of TiN used for protective layers. Then we expected that atmospheric pressure glow (APG) plasma will become a new metal treatment method, and we examined about nitriding of Ti by APG plasma.

We used a capacity-coupled plasma chamber. The distance of the electrodes was 3 mm. A Ti sample was treated by the He / N2 / H2 RF plasma at an atmospheric pressure. XPS measured the depth profiles of TiN layer. The hardness was estimated with scratch test.

Etching profiles of treated Ti sheets showed that the ratios of nitrogen at the near surface increased with increasing the treatment time, but that they were about 50 % in the bulk. This suggested that TiN was formed in the bulk. The hardness increased linearly with increasing the thickness of TiN. Therefore we considered that APG plasma is effective means for surface treatment of titanium. Now, to research more details, we examine the influences of discharge power and use of NH3 as a reactive gas on the depth and the hardness of TiN layer.